Anatomy of the brain

The brain stem sits at the base of the brain and connects to the top of your spine. It maintains important body functions such as breathing, swallowing, digestion, eye movement and your heartbeat. Strokes in the brain stem are often fatal, but when they are not, they affect many of these functions.

The cerebellum is located at the bottom of the brain, at the back of your head. It is attached to the back of the brain stem, and looks like a miniature brain. It helps control some automatic responses and behaviours, simple movements such as picking up a small object, and more complicated tasks such as balancing. A stroke in this part of the brain could cause a lack of coordination, clumsiness, shaking or other movement disorders.

Also known as the "thinking brain," the cerebrum is the main, bulky part of your brain. This is where thinking and muscle control occurs. The cerebrum is made of two halves or hemispheres. Each hemisphere is divided into portions called lobes.

Usually, one of these hemispheres is slightly more developed and is called the dominant side. The dominant side is where written and spoken language is organized. In almost all of us, the left hemisphere is dominant even if you are right handed. Because the nervous system is set up in a cross-over design, the right side of your brain controls the left side of your body, and vice versa.

Right hemisphere: The right side of the brain controls artistic functions such as music, awareness of art and insight. It also controls the ability to understand spatial relations, recognize faces and focus your attention on something. People with a stroke on the right side may have trouble with these functions.

Left hemisphere: The left side of the brain is responsible for scientific function, such as the ability to work with numbers and reasoning. It also is largely responsible for the ability to understand spoken language and the written word.

The lobes : The entire cerebrum is made up of two layers. The outermost layer is called the cerebral cortex (gray matter). The other layer, called cortex is deeply wrinkled and three of the deepest folds are used to divide the hemispheres into four distinct areas or lobes.

Frontal lobe: In each hemisphere, the frontal lobe is responsible for movement (motor functions), decision making and executive control (selection and co-ordination of goal-directed behaviors). A stroke in the right side of the frontal lobe will affect your ability to move the left side of your body, and vice versa. Damage to the frontal lobe (usually on the left hemisphere) can cause Broca's aphasia and you can find it difficult to speak in complete sentences.

Parietal lobe: Behind the frontal lobe lies the parietal lobe. It is concerned mainly with sensory activities, such as receiving and interpreting information from all parts of the body, including where your body is positioned in physical space . A stroke affecting the parietal lobe in the right hemisphere can cause agnosia, which means you can feel, see and hear, but may not be able to understand what you are perceiving. In other cases, a condition called neglect may develop, which means you may lack awareness of one side of your body. Neglect can impair many self care skills, such as dressing and washing.

Temporal lobe: The temporal lobe controls hearing and memory and is also involved with auditory perception. Strokes in the temporal lobe of the dominant hemisphere (usually the left) can cause a speech disorder known as Wernicke’s aphasia. People with Wernicke's aphasia (fluent aphasia) may speak in long sentences that have no meaning, or with unnecessary words and made-up words. Memories are stored in the inner part of the temporal lobe. Unless both the left and right lobes are damaged, memory loss after stroke is usually temporary.

Occipital lobe: The occipital lobe lies at the back of the head and is responsible for vision. A stroke in the occipital lobe on one side may result in vision loss on the opposite side. Although the eye is functioning normally, the brain is unable to process information from that eye.